1. Field of the Invention
The present invention relates to footwear, and in particular, to a protective sole construction for a work boot or shoe, hiking boot or the like.
2. Description of the Prior Art
This type of footwear, generally referred to as protective footwear, is subject to stringent requirements and is usually constructed with a steel toe cap and a stainless steel alloy mid-sole to resist sole penetration by nails, etc. The stainless steel alloy mid-sole must be accurately positioned and embedded in the sole made of a material such as a nitrile rubber. It is also preferable in such sole constructions to provide a heel filler plug which will reduce the volume of nitrile rubber utilized and thus the time required to vulcanize it. By selecting a suitable plug, the heel can also be made more rigid. In addition to the above elements, it is required to have an insole above the mid-sole in the sole construction. The insole should be somewhat flexible and can be made of a suitable plastics material.
U.S. Pat. No. 4,404,757, Sweeny, Sept. 20, 1983, attempts to solve many of the above problems by providing a molded heel plug with projections for anchoring a steel mid-sole. The Sweeny sole comprises three pieces, including an insole, which must be located on the last before the sole material can be molded thereto.